2008 Barcelona - European Society of Human Genetics

Clinical genetics
DNA banked from 80 XLMR families and 30 male sib-ships that are
negative for mutations in the most common XLMR associated genes
(FMR1 CGG expansion and ARX mutations) . This group of patients
was stratified into a smaller cohort of subjects according to the clinical
criteria indicated above. Preliminary findings involving qPCR analyses,
suggests significant MECP2 involvement in XLMR patient phenotypes
.
This study further assesses the degree of MECP2 involvement in an
XLMR cohort of South African patients using MLPA analysis of the
MECP2 chromosomal region in a larger group of XLMR patients .
Determining the proportion of XLMR patients in the Human Genetics
bank, due to MECP2 mutations will assist in the genetic management
of XLMR families through definitive diagnostic systems, carrier ascertainment
and prenatal diagnoses to carrier females .
P01.104
mEcP2 gene mutation analysis in patients with Rett-like features
in Latvia
N. Pronina1,2 , O. Sterna1,2 , D. Bauze1 , Z. Krumina1 , B. Lace1,2 , D. Locmele1 , Z.
Daneberga1,2 , R. Lugovska1,2 ;
1 2 Children’s University Hospital; Medical Genetics Clinic, Riga, Latvia, Riga
Stradins University, Riga, Latvia.
Rett syndrome (RTT), an X-linked dominant neurodevelopmental
disorder mostly in females, with an incidence of 1 in 10 000-15 000
female births . Gene MECP2 (methyl-CpG-binding protein) gene has
been identified as the disease-causing. RTT is one of the most common
causes of mental retardation in females . After a period of normal
development usually until 6-18 months of age, affected girls enter a
period of regression, losing speech and motor skills, coincident with
the onset of hand stereotypies, leading to loss of purposeful hand use,
which is the hallmark of the disorder .
MECP2 gene is located on chromosome Xq28 and is subject to X-inactivation.
Gene mutations are identifiable in 80% of classic Rett syndrome,
but less frequently in atypical RTT .
First 10 unrelated patients (including 2 boys) with developmental delay
and autistic features were referred for molecular diagnostic . Genomic
DNA was extracted from blood leukocytes . MECP2 coding exons 2, 3,
and partly exon 4, were amplified in 7 overlapping PCR fragments and
analyzed by direct sequencing on ABI 310 genetic analyzer . No previously
reported mutations were found in analyzed fragments . Studies
of remaining part of MECP2 gene exon 4 for most common mutations
in TRD domain are in progress . Additional mutation analysis of exon 1
will be performed after exons 2, 3 and 4 complete investigation . Novel
changes found in MECP2 gene exon 4 should be confirmed by restriction
analysis .
P01.105
Analysis of polymorphisms in 5-Htt, HsP 70-1, APOE, and
HmOX-1 genes as potential modulation factors of Rett syndrome
phenotype
D. Zahorakova 1 , A. Puchmajerova 1 , L. Kralik 1 , M. Jachymova 2 , A. Baxova 3 , J.
Zeman 1 , P. Martasek 1 ;
1 Department of Pediatrics and Center for Applied Genomics, General University
Hospital and First School of Medicine Charles University, Prague, Czech Republic,
2 Institute of Clinical Biochemistry and Laboratory Diagnostics, General
University Hospital and First School of Medicine Charles University, Prague,
Czech Republic, 3 Institute of Biology and Clinical Genetics, General University
Hospital and First School of Medicine Charles University, Prague, Czech Republic.
Background: Rett syndrome is a severe X-linked neurodevelopmental
disorder caused primarily by de novo mutations in the MECP2 gene .
It is one of the leading causes of mental retardation in females with
prevalence 1:10,000 female births worldwide . The phenotypic spectrum
of Rett syndrome is very variable even in females with random
X chromosome inactivation . Therefore we hypothesize there might be
other genetic factors which modulate the Rett phenotype . In a large
case-control study, we performed molecular genetic analysis of functional
polymorphisms in several genes involved in neuronal development
and metabolism (5-HTT, HSP70-1, APOE, and HMOX-1) .
Methods: All patients carried confirmed pathogenic mutation in the
MECP2 gene . Molecular genetic analysis of six polymorphisms was
performed using PCR-based methods (PAGE, PCR/RFLP) . Results
were statistically evaluated by the test of binomical distribution .
Results: Our findings revealed a statistically significant difference between
patients and controls for allele and/or genotype distribution of
APOE, 5-HTT, and HSP70-1 (-110A>C), but not for associations between
Rett syndrome and polymorphisms (GT)n in the HMOX-1 promoter
or +190C>G in HSP70-1 .
Conclusion: To our knowledge this is the first such study in Rett syndrome
patients and further confirmation in experimental and epidemiological
studies is necessary . Understanding the inherited factors that
influence patients’ susceptibility for developing various Rett phenotypes
may lead to the development of better and more comprehensive
therapies .
The study was supported by grants GA UK 257927 92707, IGA MZ
NR9215, and MSM0021620849 .
P01.106
CDKL5 gene mutations in patients with a RTT-like phenotype
N. Puente-Unzueta1 , C. Martínez-Bouzas1 , E. Beristain1 , N. Viguera1 , J. Prats1 ,
A. García-Rives1 , M. T. Calvo2 , M. Salido3 , M. I. Tejada1 ;
1 2 Hospital de Cruces, Barakaldo-Bizkaia, Spain, Hospital Universitario Miguel
Servet, Zaragoza, Spain, 3Hospital del Mar, Barcelona, Spain.
Rett Syndrome (RTT) is a progressive neurodevelopmental disorder
showing several phenotypic manifestations . The majority of clinically
diagnosed cases have been found to show a mutation in the MECP2
X-linked gene, a gene that encodes for a transcription suppressor
Methyl-CpG-Binding Protein . The cyclin-dependent kinase-like 5 gene
(CDKL5) is another X-linked gene that belongs to the same molecular
pathway of MECP2 and encodes a phosphorylated protein with protein
kinase activity . Mutations in the CDKL5 gene cause severe mental retardation,
early onset epilepsy and drug resistance .
We have screened the 21 exons of the CDKL5 for mutations in 18 female
patients with a RTT-like phenotype and epilepsy who had tested
negative for MECP2 mutations . The aim of this study was to determine
whether the condition of these patients is due to mutations in the
CDKL5 gene . Genomic DNA was extracted using standard procedures
from the peripheral blood leukocytes of patients . Mutation analyses
were performed using CSGE in 24 fragments of the CDKL5 gene and
sequenced in case of anomalous bands .
We have only found 2 cases with variations: three nucleotide exchanges
that form a rare conserved haplotype - IVS4+17A>G, c .3003C>T
(H1001H) and c .3084G>A (T1028T) (J Tao et al . 2004) - in one patient
and a new missense change in the 17th exon - c .2389G>A (D797N)
- in another patient without pathologic effect because the father was
the carrier .
These results indicate that mutations in the CDKL5 gene are not an
important contribution in the ethiology of RTT with epilepsy in our
population .
P01.107
Searching for Copy Number Polymorphisms as modifiers in RTT
syndrome
R. Artuso1 , F. Ariani1 , A. Spanhol Rosseto1 , D. Rondinella1 , F. T. Papa1 , E.
Katzaki1 , M. A. Mencarelli1 , I. Meloni1 , F. Mari1 , M. Pollazzon1 , M. Zappella2 , G.
Hayek2 , A. Renieri1 ;
1 2 Medical Genetics, Siena, Italy, Child Neuropsychiatry, University hospital,
Siena, Italy.
MECP2 mutations are associated with a broad spectrum of clinical
phenotypes in girls, including the preserved speech variant (PSV) of
RTT . In this variant, girls improve language and motor abilities . Previous
studies demonstrated that mutation type and/or X chromosome
inactivation are not sufficient to explain such variability, suggesting
that additional factors are involved . We hypothesized that Copy Number
Polymorphisms (CNPs) contribute to RTT clinical variability . We
started to search such variations in three familial cases with the same
MECP2 mutation and different phenotype (http://www .biobank .unisi .
it): two pairs of sisters (one classic and the other PSV) and a mother/
daughter pair (mother with mental retardation and daughter with classic
RTT) . In these cases, we performed whole genome array-CGH
and we found a total of 18 CNPs . Three of them (6p21 .33, 8p11 .23,
14q11) are in common between two familial cases . Interestingly, the
8p11 .23 region includes ADAM5 . ADAMs are transmembrane proteins
that play an important role in the development of the nervous system .
They regulate proliferation, migration, differentiation and survival of
various cells, as well as axonal growth and myelination . Among the